A routing protocol based on node density for ad hoc networks:
Abstract:
Ad hoc networks are a type of mobile network that functions without any fixed infrastructure. One of the weaknesses of ad hoc networks is that a route used between a source and a destination is likely to break during communication. To solve this problem, one approach consists of selecting routes whose nodes have the most stable behavior. Another strategy aims at improving the route repair procedure. This paper proposes a method for improving the success rate of local route repairs in mobile ad hoc networks. This method is based on the density of the nodes in the neighborhood of a route and on the availability of nodes in this neighborhood. Theoretical computation and simulation results show that the data packet loss rate decreased significantly compared to other methods which are well documented in the literature. In addition, the time required to complete a local route repair following a failure was significantly reduced.
1. Introduction
In recent years, we have witnessed considerable accomplishments in the design, development, and
deployment of wireless communication networks. Personal and mobile communications are made
possible by the convergence of several different technologies, specifically computer networking
protocols, wireless/mobile communication systems, distributed computing and Internet [6,14,25].
The mixed wired and wireless network topologies that are becoming so common, including fixed and
ad-hoc connection types, create the need to rationally exploit dynamically variable routing as a
function of network conditions [10]. At the same time, a phenomenal growth in data traffic and a wide range of new requirements of emerging applications call for new mechanisms for the control and management of communication networks [20]. The emergence of real-time applications and the widespread use of wireless and mobile devices have generated the need to provide quality of service (QoS) support in wireless and mobile networking environments [24].
A mobile ad hoc network (MANETs) is a mobile wireless network composed of several mobile
nodes, likely to communicate among themselves without the intervention of any centralized management or existing infrastructure. Hence, these mobile nodes must necessarily be able to cooperate to allow communication between themselves. Their main asset resides in the fact that they are not tributary to fixed installations.
2. Background and related work
A routing protocol is the mechanism by which user traffic is directed and transported through the
network from a source node to a destination node. The objectives include maximizing network performance from an application point of view, while minimizing the cost imposed on the network in
terms of capacity. QoS routing is an essential part of a QoS architecture. It is a routing mechanism
under which paths for flows are determined on the basis of some knowledge of the resources available in the network as well as on the QoS requirements of the flows or connections [24].
Resource reservation is necessary for providing guaranteed end-to-end performance for multimedia
applications. However, resource reservation is supported neither in the present Internet nor in mobile ad hoc networks. Also, the data packets sent by these applications could follow different paths and reach the destination out of order, which is not desirable. The current routing protocols used in IP networks are transparent to any particular QoS that different flows could require. As a result, routing decisions are made without referring to the QoS requirements of the flow. This means that flows are often routed over paths that are unable to support their requirements while alternate paths with sufficient resources exist. This will increase the call blocking probability. Hence, the goal of QoS routing algorithms is to find a path in the network that satisfies the given requirements [13,19,20].
.
.
.
.
When a mobile station A initiates communication with a mobile station B, A can easily reach B
through the information included in its routing table. In order to update a node’s routing table in
a context of dynamic topological changes, each node in the network periodically sends an update
message with routing information to its neighbors. Updates depend on two criteria: periodicity of
updates and events occurrence, such as the arrival of a new node in the neighborhood. Its goal is to
make it possible for a mobile host to locate any other unit in the network at any time. These updates
can be carried out either in a complete or an incremental way. The main weakness of this protocol
is the enormous bandwidth consumed by routing traffic control. Furthermore, DSDV is
slow; a mobile unit must wait to receive routing information to update the corresponding entry in
its routing table.
.
.
.
.
Global route repair: If a link failure were detected during the transmission of a packet from
source A to destination B, the node that detected the failure would return an error message to the
source. Then, the source initiates a new route discovery phase to find a new path between A and
B. This phase requires much time to complete and overloads the network with many routing messages. This results in bandwidth waste that is detrimental to the overall performance of the
network.
Local route repair: When a node detects a link failure, it does not systematically send an error
message to the source. First, it attempts to repair the route itself. It only sends an error message to
the source if this first attempt fails. Consider the case presented in Fig. 1. Step (a) represents the
route before failure detection. In step (b), Node D detects a link failure between D and G. According
to the local route repair procedure of step (c), D diffuses a route request (RREQ) packet which is
propagated across the network. When it receives this packet, J returns a route reply (RREP) packet
to D. This packet is forwarded by I, G and F. When D finally receives it, the route is repaired and communication can carry on.
5. Conclusion
The routing method presented in this paper aims to improve QoS management in MANETs by
taking into account the density of a node, defied as the number of mobile units available in the radio
range of the node. Our approach was based on a thorough analysis of the available mechanisms and tools that take into account quality of service in ad hoc networks. Then, we introduced the concept of
density and described how the network could exploit this information to improve the QoS offered.
The method can be subdivided into two parts: a selection mechanism that chooses the most robust
route available, and a mechanism to forecast the failure of a local route repair before it occurs.
The route selection mechanism described aims at selecting among several routes, the one whose
maintenance is the easiest to realize. The simulation results confirmed our hypothesis: the duration
of a route repair after a failure is improved. In addition, our mechanism drastically reduced the
data packet loss rate.
We also highlighted a situation where an attempt to repair a route locally could be useless and even harmful for the network: if the density around the node which initiated the local route repair is too low, the route repair procedure is bound to fail. In this situation, it is preferable to turn over directly to the source after having detected the failure of the link and to proceed to a global route repair. To validate our work, we implemented our improvements of the AODV protocol in Opnet Modeler. Then, we tested our protocol for a given configuration. The results obtained are encouraging: the data packet loss rate is strongly reduced compared to the initial version. In addition, the time required to complete a local route repair following a failure decreased significantly.
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Abstract:
Ad hoc networks are a type of mobile network that functions without any fixed infrastructure. One of the weaknesses of ad hoc networks is that a route used between a source and a destination is likely to break during communication. To solve this problem, one approach consists of selecting routes whose nodes have the most stable behavior. Another strategy aims at improving the route repair procedure. This paper proposes a method for improving the success rate of local route repairs in mobile ad hoc networks. This method is based on the density of the nodes in the neighborhood of a route and on the availability of nodes in this neighborhood. Theoretical computation and simulation results show that the data packet loss rate decreased significantly compared to other methods which are well documented in the literature. In addition, the time required to complete a local route repair following a failure was significantly reduced.
1. Introduction
In recent years, we have witnessed considerable accomplishments in the design, development, and
deployment of wireless communication networks. Personal and mobile communications are made
possible by the convergence of several different technologies, specifically computer networking
protocols, wireless/mobile communication systems, distributed computing and Internet [6,14,25].
The mixed wired and wireless network topologies that are becoming so common, including fixed and
ad-hoc connection types, create the need to rationally exploit dynamically variable routing as a
function of network conditions [10]. At the same time, a phenomenal growth in data traffic and a wide range of new requirements of emerging applications call for new mechanisms for the control and management of communication networks [20]. The emergence of real-time applications and the widespread use of wireless and mobile devices have generated the need to provide quality of service (QoS) support in wireless and mobile networking environments [24].
A mobile ad hoc network (MANETs) is a mobile wireless network composed of several mobile
nodes, likely to communicate among themselves without the intervention of any centralized management or existing infrastructure. Hence, these mobile nodes must necessarily be able to cooperate to allow communication between themselves. Their main asset resides in the fact that they are not tributary to fixed installations.
2. Background and related work
A routing protocol is the mechanism by which user traffic is directed and transported through the
network from a source node to a destination node. The objectives include maximizing network performance from an application point of view, while minimizing the cost imposed on the network in
terms of capacity. QoS routing is an essential part of a QoS architecture. It is a routing mechanism
under which paths for flows are determined on the basis of some knowledge of the resources available in the network as well as on the QoS requirements of the flows or connections [24].
Resource reservation is necessary for providing guaranteed end-to-end performance for multimedia
applications. However, resource reservation is supported neither in the present Internet nor in mobile ad hoc networks. Also, the data packets sent by these applications could follow different paths and reach the destination out of order, which is not desirable. The current routing protocols used in IP networks are transparent to any particular QoS that different flows could require. As a result, routing decisions are made without referring to the QoS requirements of the flow. This means that flows are often routed over paths that are unable to support their requirements while alternate paths with sufficient resources exist. This will increase the call blocking probability. Hence, the goal of QoS routing algorithms is to find a path in the network that satisfies the given requirements [13,19,20].
.
.
.
.
When a mobile station A initiates communication with a mobile station B, A can easily reach B
through the information included in its routing table. In order to update a node’s routing table in
a context of dynamic topological changes, each node in the network periodically sends an update
message with routing information to its neighbors. Updates depend on two criteria: periodicity of
updates and events occurrence, such as the arrival of a new node in the neighborhood. Its goal is to
make it possible for a mobile host to locate any other unit in the network at any time. These updates
can be carried out either in a complete or an incremental way. The main weakness of this protocol
is the enormous bandwidth consumed by routing traffic control. Furthermore, DSDV is
slow; a mobile unit must wait to receive routing information to update the corresponding entry in
its routing table.
.
.
.
.
Global route repair: If a link failure were detected during the transmission of a packet from
source A to destination B, the node that detected the failure would return an error message to the
source. Then, the source initiates a new route discovery phase to find a new path between A and
B. This phase requires much time to complete and overloads the network with many routing messages. This results in bandwidth waste that is detrimental to the overall performance of the
network.
Local route repair: When a node detects a link failure, it does not systematically send an error
message to the source. First, it attempts to repair the route itself. It only sends an error message to
the source if this first attempt fails. Consider the case presented in Fig. 1. Step (a) represents the
route before failure detection. In step (b), Node D detects a link failure between D and G. According
to the local route repair procedure of step (c), D diffuses a route request (RREQ) packet which is
propagated across the network. When it receives this packet, J returns a route reply (RREP) packet
to D. This packet is forwarded by I, G and F. When D finally receives it, the route is repaired and communication can carry on.
5. Conclusion
The routing method presented in this paper aims to improve QoS management in MANETs by
taking into account the density of a node, defied as the number of mobile units available in the radio
range of the node. Our approach was based on a thorough analysis of the available mechanisms and tools that take into account quality of service in ad hoc networks. Then, we introduced the concept of
density and described how the network could exploit this information to improve the QoS offered.
The method can be subdivided into two parts: a selection mechanism that chooses the most robust
route available, and a mechanism to forecast the failure of a local route repair before it occurs.
The route selection mechanism described aims at selecting among several routes, the one whose
maintenance is the easiest to realize. The simulation results confirmed our hypothesis: the duration
of a route repair after a failure is improved. In addition, our mechanism drastically reduced the
data packet loss rate.
We also highlighted a situation where an attempt to repair a route locally could be useless and even harmful for the network: if the density around the node which initiated the local route repair is too low, the route repair procedure is bound to fail. In this situation, it is preferable to turn over directly to the source after having detected the failure of the link and to proceed to a global route repair. To validate our work, we implemented our improvements of the AODV protocol in Opnet Modeler. Then, we tested our protocol for a given configuration. The results obtained are encouraging: the data packet loss rate is strongly reduced compared to the initial version. In addition, the time required to complete a local route repair following a failure decreased significantly.
DOWNLOAD LINK:
CLICK ME
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